BackgroundAngiopoietin like‐2 (angptl2), a proinflammatory protein, is overexpressed in endothelial cells (ECs) from patients with coronary artery disease (CAD). Whether angptl2 contributes to atherogenesis is unknown. We tested the hypothesis that angptl2 promotes inflammation and leukocyte adhesion onto ECs, thereby accelerating atherogenesis in preatherosclerotic dyslipidemic mice.Methods and ResultsIn ECs freshly isolated from the aorta, basal expression of TNF‐α and IL‐6 mRNA was higher in 3‐month‐old severely dyslipidemic mice (LDLr−/−; hApoB100+/+ [ATX]) than in control healthy wild‐type (WT) mice (P<0.05) and was increased in both groups by exogenous angptl2 (100 nmol/L). Angptl2 stimulated the adhesion of leukocytes ex vivo on the native aortic endothelium of ATX, but not WT mice, in association with higher expression of ICAM‐1 and P‐selectin in ECs (P<0.05). Antibodies against these endothelial adhesion molecules prevented leukocyte adhesion. Intravenous administration of angptl2 for 1 month in preatherosclerotic 3‐month‐old ATX mice increased (P<0.05) total cholesterol and LDL‐cholesterol levels, strongly induced (P<0.05) the expression of endothelial proinflammatory cytokines and adhesion molecules while accelerating atherosclerotic lesion formation by 10‐fold (P<0.05). Plasma and aortic tissue levels of angptl2 increased (P<0.05) with age and were higher in 6‐ and 12‐month‐old ATX mice than in age‐matched WT mice. Angptl2 accumulated to high levels in the atherosclerotic lesions (P<0.05). Finally, angptl2 was greatly expressed (P<0.05) in ECs cultured from CAD patients, and circulating angptl2 levels were 6‐fold higher in CAD patients compared with age‐matched healthy volunteers.ConclusionsAngptl2 contributes to the pathogenesis of atherosclerosis.

The cardiac cycle imposes a mechanical stress that dilates elastic carotid arteries, while shear stress largely contributes to the endothelium-dependent dilation of downstream cerebral arteries. In the presence of dyslipidemia, carotid arteries stiffen while the endothelial function declines. We reasoned that stiffening of carotid arteries would be prevented by reducing resting heart rate (HR), while improving the endothelial function would regulate cerebral artery compliance and function. Thus we treated or not 3-mo-old male atherosclerotic mice (ATX; LDLr(-/-):hApoB(+/+)) for 3 mo with the sinoatrial pacemaker current inhibitor ivabradine (IVA), the β-blocker metoprolol (METO), or subjected mice to voluntary physical training (PT). Arterial (carotid and cerebral artery) compliance and endothelium-dependent flow-mediated cerebral dilation were measured in isolated pressurized arteries. IVA and METO similarly reduced (P < 0.05) 24-h HR by ≈15%, while PT had no impact. As expected, carotid artery stiffness increased (P < 0.05) in ATX mice compared with wild-type mice, while cerebral artery stiffness decreased (P < 0.05); this paradoxical increase in cerebrovascular compliance was associated with endothelial dysfunction and an augmented metalloproteinase-9 (MMP-9) activity (P < 0.05), without changing the lipid composition of the wall. Reducing HR (IVA and METO) limited carotid artery stiffening, but plaque progression was prevented by IVA only. In contrast, IVA maintained and PT improved cerebral endothelial nitric oxide synthase-dependent flow-mediated dilation and wall compliance, and both interventions reduced MMP-9 activity (P < 0.05); METO worsened endothelial dysfunction and compliance and did not reduce MMP-9 activity. In conclusion, HR-dependent mechanical stress contributes to carotid artery wall stiffening in severely dyslipidemic mice while cerebrovascular compliance is mostly regulated by the endothelium.

Renal and lung fibrosis was characterized by the accumulation of collagen-immunoreactive mesenchymal cells expressing the intermediate filament protein nestin. The present study tested the hypothesis that nestin expression was increased in the hypertrophied/fibrotic left ventricle of suprarenal abdominal aorta constricted adult male Sprague-Dawley rats and induced in ventricular fibroblasts by pro-fibrotic peptide growth factors. Nestin protein levels were upregulated in the pressure-overloaded left ventricle and expression positively correlated with the rise of mean arterial pressure. In sham and pressure-overloaded hearts, nestin immunoreactivity was detected in collagen type I(+)-and CD31(+)-cells identified in the interstitium and perivascular region whereas staining was absent in smooth muscle α-actin(+)-cells. A significantly greater number of collagen type I(+)-cells co-expressing nestin was identified in the left ventricle of pressure-overloaded rats. Moreover, an accumulation of nestin(+)-cells lacking collagen, CD31 and smooth muscle α-actin staining was selectively observed at the adventitial region of predominantly large calibre blood vessels in the hypertrophied/fibrotic left ventricle. Angiotensin II and TGF-β1 stimulation of ventricular fibroblasts increased nestin protein levels via phosphatidylinositol 3-kinase- and protein kinase C/SMAD3-dependent pathways, respectively. CD31/eNOS(+)-rat cardiac microvascular endothelial cells synthesized/secreted collagen type I, expressed prolyl 4-hydroxylase and TGF-β1 induced nestin expression. The selective accumulation of adventitial nestin(+)-cells highlighted a novel feature of large vessel remodelling in the pressure-overloaded heart and increased appearance of collagen type I/nestin(+)-cells may reflect an activated phenotype of ventricular fibroblasts. CD31/collagen/nestin(+)-interstitial cells could represent displaced endothelial cells displaying an unmasked mesenchymal phenotype, albeit contribution to the reactive fibrotic response of the pressure-overloaded heart remains unknown.

The present study tested the hypothesis that vessel remodeling secondary to hypertension was characterized by nestin upregulation in vascular smooth muscle cells. Two weeks after suprarenal abdominal aorta constriction of adult male Sprague-Dawley rats, elevated mean arterial pressure increased the media area and thickness of the carotid artery and aorta and concomitantly upregulated nestin protein levels. In the normal adult rat carotid artery, nestin immunoreactivity was observed in a subpopulation of vascular smooth muscle cells, and the density significantly increased following suprarenal abdominal aorta constriction. Filamentous nestin was detected in cultured rat carotid arteryand aorta-derived vascular smooth muscle cells and an analogous paradigm observed in human aorta-derived vascular smooth muscle cells. ANG II and EGF treatment of vascular smooth muscle cells stimulated DNA and protein synthesis and increased nestin protein levels. Lentiviral short-hairpin RNA-mediated nestin depletion of carotid artery-derived vascular smooth muscle cells inhibited peptide growth factor-stimulated DNA synthesis, whereas protein synthesis remained intact. These data have demonstrated that vessel remodeling secondary to hypertension was characterized in part by nestin upregulation in vascular smooth muscle cells. The selective role of nestin in peptide growth factor-stimulated DNA synthesis has revealed that the proliferative and hypertrophic responses of vascular smooth muscle cells were mediated by divergent signaling events. nestin; carotid artery; aorta; hypertension; vascular remodeling DURING THE DEVELOPMENT of the central nervous system (CNS), a population of neuroepithelial stem cells was initially identified via expression of the intermediate filament protein nestin (8,18). Nestin is a 240-kDa protein and a member of the class VI family of intermediate filament proteins, and, in contrast to other classes, it is unable to self-assemble and form homodimers because of a short NH 2 terminus (37, 39). Therefore, nestin will form heterodimers with other intermediate filament proteins, including vimentin and desmin (37). The promoter region upstream of exon 1 of the nestin gene does not contain any identifiable elements regulating expression. However, the nestin gene does contain regulatory elements in the various intron regions that drive expression in a cell-specific manner (37). In neural progenitor/stem cells, nestin expression is independently regulated by restricted enhancer elements identified in the second intron (43). In humans, a highly conserved region that directed expression was also identified in the second intron of the nestin gene (21). However, nestin expression driven by the second intron was not limited to CNSresident stem cells, since a transgenic mouse containing the 5.8-kb fragment of the promoter region and the 1.8-kb fragment of the second intron of the rat nestin gene linked to the reporter green fluorescent protein (GFP) identified progenitor/ stem cell populations in the skin, skeletal mus...